H. S. YADAVA and K. R. LAUMAS

Summary.

The effect of long-term oral administration of norethynodrel and 17α-ethynyl oestradiol-3-methyl ether (mestranol, EO3Me) on biochemical changes in the uterus, ovary and adrenal of rabbits has been studied. It was found that the administration of norethynodrel significantly increased the incorporation of [U-14C]glucose into lipid, RNA and protein of the rabbit uterus. In this respect, the effect of norethynodrel resembled that of an oestrogenic compound besides its known progestational action. EO3Me increased glucose metabolism and its incorporation into lipid and RNA in the uterus. Norethynodrel also increased lipid and protein synthesis in the ovary, but EO3Me enhanced only lipid synthesis in the ovary. Glucose metabolism was markedly depressed in the adrenal gland after the administration of norethynodrel. The mode of action of norethynodrel has been discussed in relation to the disturbance in the biochemical changes it produced in the uterus and the ovary.

K. R. LAUMAS and H. S. YADAVA

Summary.

This paper reports studies on the incorporation of [U-14C]glucose into lipid, RNA and proteins of the rat uterus in the presence of an IUD after treatment with oestrogen and progesterone and on Day 5 of pregnancy at the time of implantation. The results show that there is an increase in the incorporation of [U-14C]glucose into lipid, RNA and proteins in the IUD horn compared with that of the control horn of ovariectomized and oestrogen-treated animals. The increase in weight of the IUD horn compared with the control horn can be interpreted as due to an increased oestrogen-like response by the uterus in the presence of an IUD. This response may be caused by oestrogens, histamines or other amines.

A significant decrease in the incorporation of [U-14C]glucose into lipid, RNA and proteins of the IUD horn compared with the control horn was found on treatment of the animals with oestrogen+progesterone and progesterone alone for 6 hr. Treatment of the animals for 9 days with oestrogen+progesterone also significantly depressed the rate of protein synthesis in the IUD horn compared with the control horn. On Day 5 of pregnancy at the time of implantation, there was a statistically significant decrease in the incorporation of [U-14C]glucose into lipid, RNA and proteins of the IUD horn compared with the control horn. These experiments indicated an increased sensitivity of the uterus to progesterone in the presence of an IUD.

The uterus shows an increased oestrogen-like response in the presence of an IUD. The increased sensitivity of the uterus to progesterone at the time of implantation produces asynchronous changes in the uterus and results in an anti-implantation effect of the IUD. The mode of action of an IUD in the light of these observations is discussed.